In graphic arts reproduction processes the original image appearing to have EL continuous tone gradation is reproduced by a collection of a large number of dots and/or lines, either by optical means in the case of a camera film, or by electronic means in case of a recorder film. The tone of the reproduced image is influenced by both the size of the dots and lines and their density. A graphic arts film exposed in a way to exactly render the relative proportions of black and white in the original must produce dots and lines of sufficient density; another reason herefore is the fact that no substantial amount of copying light may be transmitted through the dots and lines in a further duplicating cycle or during the direct exposure of a printing plate. Therefore a photographic element showing high contrast or so-called "lith gradation" on development is highly desired. Furthermore the generated or reproduced dots and lines must exhibit a well-shaped form and sharp edges.
This most desired combination of high contrast and excellent dot quality is commonly termed "lith quality". The goal of achieving optimal lith quality is reached by the combination of specially designed graphic arts material and appropriate processing systems. A 30 first group of such processing systems consists of the traditional "lith developers" characterized by the presence of hydroquinone as the sole developing agent and a low but critical sulphite ions content giving rise to an infectious development mechanism, as was described by Yule in The Journal of the Franklin Institute, Vol. 239, p. 221-223, (1945). This type of development is believed to proceed autocatalytically. The low concentration of sulphite is maintained by the progressive dissociation of an aldehyde-bisulphite adduct. However these conventional lith developers are rather instable in time and require complicated replenishment systems for both oxidation and exhaustion. Furthermore their developing capacity is limited due to the fact that they contain hydroquinone as the sole developing agent.
In more recent times so-called "hard dot Rapid Access" developers were introduced on the market which combine a good stability with a "lith quality" in the reproduction of lines and screen dots. Examples of such developers and corresponding appropriate photographic materials include the GRANDEX system, marketed by FUJI PHOTO ltd., AGFASTAR, marketed by AGFA-GEVAERT N.V. and the ULTRATEC system, marketed by EASTMAN KODAK Co. Some of these systems make use of the contrast promoting action, induced by a nucleating mechanism, of hydrazine derivatives known for long time in the photographic art. As described by Simson et al., U.S. Pat. No. 4,650,746, use of a hydrazine compound permits the use of an auxiliary development agent in combination with the hydroquinone type of developing agent so that the development capacity can be increased. It also permits the presence of a relatively high sulphite concentration in order to protect the developer against aerial oxidation and thereby prolonging its effective working life. Further early disclosures on hydrazine compounds, incorporated either in a photographic element or in a developing solution, include Smith U.S. Pat. No. 2,410,690, Stauffer U.S. Pat. No. 2,419,974, Trivelli U.S. Pat. No. 2,419,975 and Hunsberger U.S. pat. No. 2,892,715 and an article by Stauffer, Smith and Trivelli entitled "The influence of photographic developers containing hydrazine upon the characteristic curves of photographic materials", The Journal of the Franklin Institute, Vol. 238, p. 291-298, October 1944. Since then the photographic world has undertaken extensive research on hydrazine chemistry for use in photographic applications and the recent patent literature on new hydrazine derivatives and on the combination of known or new hydrazines with other useful ingredients in photographic elements or developers is abundant.
A practical early recognized problem was caused by the high pH levels needed for the developers containing hydrazine compounds or used with photographic elements containing these compounds in order to get the maximum effect on contrast. The teaching of Nothnagle U.S. Pat. No. 4,269,929 brought a solution to this problem. Here a method for high contrast development was disclosed involving a hydrazine compound, either in the photographic element or in the developer, said developer further containing a hydroquinone developing agent, a 3-pyrazolidinone developing agent, sulphite ions, and a "contrast-promoting amount" of an amino compound. In a preferred embodiment the hydrazine compound was incorporated in the photographic material. According to this patent, issued May 26, 1981, this particular combination of ingredients allow the use of a rather moderate alkaline pH for the developing solution while retaining the desired high contrast and dot quality characteristics. In this way an excellent combination of lith quality of the finished material, high developing capacity and long effective life of the developer was achieved.
Since then intense research has been conducted to improve the performance of hydrazines, mostly acylhydrazides, and in particular to make them workable in combination with conventional rapid access developers having a pH around 10.5 and containing no special ingredients such as amine boosters. Specific new hydrazide derivatives are described, e.g. in JP-A 57-99635, EP 0 217 310, JP-A 61-270744, JP-A 62-89958, EP 0 283 040, EP 0 301 799, U.S. Pat. No. 4,816,373, U.S. Pat. No. 4,847,180, JP-A 63-294552, JP-A 63-44649, JP-A 63-8715, EP 0 283 040, JP-A 01-100530, EP 0 345 025, JP-A 01-201650, EP 0 356 898, DE 38 29 078, U.S. Pat. No. 4,950,578, U.S. Pat. No. 5,028,510, EP 0 399 460, U.S. Pat. No. 5,006,445, JP-A 01-285940, U.S. Pat. No. 4,988,604, U.S. Pat. No. 4,994,365, JP-A 02-300474, JP-A 02-302750, JP-A 02-841, JP-A 02-947, EP 0 444 506, EP 0 479 156, JP-A 04-283743, EP 0 539 925 and U.S. Pat. No. 5,212,045.
A study on the nucleating mechanism of acylhydrazides, responsible for infectious development, can be find in Simson, SPSE, 25th Fall Symposium, (1985), p. 48. Other studies include Kitchin et al., J. Phot. SCi., Vol. 35, (1987), p. 162, Shinoara et al., J. Photogr. Sci., Vol. 35, (1987), p. 181, and Kobayashi, J. Phot. Sci., Vol. 43, (1995), p. 186.
An important technological breakthrough was the development and use of sulphonamido-arylhydrazides as disclosed in EP 0 286 840 and U.S. Pat. No. 5,104,769, which proved to be a very reactive and effective type. Another main progress was the use of hydrazides, especially sulphonamido-arylhydrazides in combination with so-called "incorporated boosters", such as disclosed in Machonkin U.S. Pat. No. 4,975,354, which can be incorporated into the photographic material itself instead of the developer. Still other graphic arts systems are based on the use of hydrazine types that can release a photographically useful group, e.g. an accelerator or a development restrainer, such as disclosed in e.g. EP 0 393 720, EP 0 393 721, EP 0 399 460, U.S. Pat. No. 5,258,259, EP 0 420 005, U.S. Pat. No. 5,252,438 and U.S. Pat. No. 5,262,274.
In European Patent Application, appl. No. 97201902 a new class of active arylhydrazides is disclosed having in ortho position a substituent comprising a pyridinium, quinolinium or isoquinolinium group. With this class of hydrazides high gradation was obtained. However, this type of hydrazides causes an important image spread leading to considerable dot growth in function of exposure intensity or time of development. In the case of a correct exposure of a 50% dot original this results in a poor quality of the small dots (5% or less).
The present invention extends the teachings on hydrazine compounds in photographic silver halide materials, and constitutes a further improvement to the teachings of European Patent Application, appl. No. 97201902, cited above.